Non-contact substrate support position sensing system and corresponding adjustments

ABSTRACT

A substrate processing system includes an optical measurement assembly coupled to an exterior of a processing chamber that has a portion that is transparent. The processing chamber includes a reference object and a pedestal for supporting a work piece. The optical measurement assembly measures a lateral location, a height and a tilt of the pedestal by transmitting light into the processing chamber through the transparent portion of the processing chamber and detecting a reflected light from both the reference object and the portion of the pedestal after the reflected light leaves the chamber through the transparent portion of the processing chamber. A method of adjusting a pedestal includes analyzing the reflected light and leveling the pedestal, translating the pedestal, calibrating the pedestal height to a preheat ring level, and checking the level and location of the pedestal in response to the analyzed reflected light.

CROSS-REFERENCES TO RELATED APPLICATIONS

The application claims the benefit of U.S. Provisional Application No.61/050,154, filed on May 2, 2008, which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND

The application relates generally to semiconductor processing equipmentand particularly to measuring the alignment of components located withinthe semiconductor processing equipment and to adjusting the position ofmisaligned components within the semiconductor processing equipment.

Semiconductor processing equipment is used in the deposition,patterning, and treatment of thin films and coatings. A conventionalsemiconductor processing system contains one or more processing chambersand a means for moving a substrate between them. A substrate may betransferred between chambers by a robotic arm which can extend to pickup the substrate, retract and then extend again to position thesubstrate in a different destination chamber. Each chamber has apedestal or some equivalent way of supporting the substrate forprocessing.

A pedestal may supply heat to a substrate during processing. Heat may beprovided by a resistive mechanism to a refractory metal coil embedded inthe heater plate. The substrate may be held by a mechanical, pressuredifferential or electrostatic means to the pedestal between when a robotarm drops off the substrate and when an arm returns to pick up thesubstrate. Lift pins are often used to elevate the wafer during robotoperations. When on the pedestal, one or more processes may beperformed. These may include annealing the substrate and depositing oretching a film on the substrate.

Most processes provide more benefit when the process uniformity acrossthe substrate surface is higher. One of the parameters which may affectuniformity is the position of the substrate during processing. As aresult, processing systems are preferably designed to providereproducible placement of substrates during processing steps.

An illustrative example of a process and associated process chamberwhich can suffer from a less than optimal reproducibility in thepedestal and substrate position is epitaxial film growth (often referredto as EPI). Deposited film uniformity (e.g. film thickness and dopantdensity) in an EPI process, as with many other processes, can besensitive to tilt and a lateral misalignment of the substrate. Theposition of the substrate is determined, in part, by the position of thepedestal.

In an EPI process, a portion of the heat supplied to the substrate maycome from optical radiation sources which expose the heater plate and/orthe substrate to light. This method is also desirable for rapid thermalprocessing and other processes which benefit from higher substratetemperatures. Substrate processing chambers designed for radiativeheating usually use quartz for some portion of the chamber wall becauseof its ability to tolerate high temperatures, low coefficient of thermalexpansion and excellent transparency to infrared and visible light. EPIchambers may employ quartz domes for the top and/or bottom of thechamber to allow the radiation to impact the substrate and pedestal. Thepedestals in EPI chambers are often called susceptors because theyabsorb radiation and provide heat to the substrate.

These quartz domes may be relied upon for support of interior chambercomponents like the pedestal, which can be a susceptor. Quartz domes areshaped at high temperatures when the glass is ductile, giving rise totolerance variabilities. FIG. 1A depicts a schematic view of an EPIchamber. The bottom quartz dome 104 is shown providing support for ashaft 108 and a rigidly affixed pedestal 112, which together may bereferred to as a substrate support assembly. The pedestal is shown inFIG. 1A indicating a non-negligible misalignment with a preheat ring 116upon assembly. The substrate support assembly is tilted about a pivotpoint 106 with an approximate location indicated near the bottom of theshaft.

A prior art technique for correcting this tilt (i.e. leveling thepedestal) is to apply a force against the shaft 108 above the pivotpoint 106 to rotate the substrate support assembly clockwise. The netresult of this technique is shown in FIG. 1B. The tilt has beencorrected, but a lateral offset has been introduced resulting in anon-uniform gap between the pedestal and the preheat ring. Note in thistwo dimensional depiction, the gap on the left 120 is larger than thegap on the right 121.

In addition to the coupling between the tilt and lateral location, thetechnique currently used has other drawbacks. The pedestal is adjustedusing a manual process that uses a contact straight-edge leveling tool.An operator using the straight-edge may visually judge the pedestalpositioning and manually adjust the tilt and/or translation mechanism ofthe pedestal until visually it appears adequate. The reliance on visualmeasurement is undesirable as it is subjective, time-consuming and proneto human errors. It also necessitates opening the chamber upper domerequiring the chamber to be vented to atmosphere which brings with it aloss in productivity due to significant down-time and recovery time.

Another drawback to the prior art technique for correcting tilt andlateral location is that the correction is done prior to pumping downthe semiconductor processing apparatus. Pumping down a semiconductorprocessing apparatus can cause components to shift, move or even flex.Components that are aligned prior to pumping down a semiconductorprocessing apparatus can become unaligned after pumping down. Forexample, a pedestal that is aligned when the semiconductor processingapparatus is opened can become misaligned for processing conditionsbecause the semiconductor processing apparatus is closed up and pumpeddown before processing. Therefore, prior art techniques for correctingtilt and lateral location have the drawback that although components canbe aligned during the alignment process, those components may becomemisaligned before or during processing of wafers.

Therefore, what is needed is a system and method for measuring andadjusting the location and tilt of a component in a semiconductorprocessing apparatus while the semiconductor processing system is fullyassembled and under vacuum. Additionally, a system and method is neededfor independently adjusting the tilt and lateral location of thecomponent.

BRIEF SUMMARY

Embodiments of the present invention relate to providing a non-contactand in-situ method to precisely measure the pedestal positioning. Thismeasurement is used as a feedback for either manual adjustment or fullyautomatic closed-loop servo based adjustment of the tilt and translationmechanism until the pedestal is fully level, centered and adjusted forheight. The non-contact method allows the measurement to be done invacuum thus eliminating the need for the chamber to be open and ventedsignificantly minimizing any down-time and recovery time.

Embodiments of the present invention provide techniques for measuringand adjusting the location and tilt of components in a semiconductorprocessing system while the semiconductor processing system is fullyassembled and under vacuum.

In embodiments of the present invention, a pedestal assembly positioningsystem is used to adjust the location and tilt of components in asemiconductor processing system. The pedestal assembly positioningsystem includes a pedestal supported by a pedestal shaft, an inner ring,a lateral adjustment assembly, and a vertical adjustment assembly. Theinner ring is rigidly attached to the pedestal and is nearly concentricwith a reference ring located on the substrate processing system. Thelateral adjustment assembly is constructed so the lateral location ofthe pedestal relative to the outer ring of the processing system isadjustable. Similarly, the vertical adjustment assembly is constructedso the tilt of the pedestal relative to the outer ring assembly of theprocessing system is adjustable. The lateral adjustment assembly andvertical adjustment assembly are coupled to the pedestal through thepedestal shaft.

In another embodiment the pedestal is a susceptor.

In yet another embodiment, the lateral adjustment assembly includesthree adjustment screws nearly equally spaced around the outer ring. Thethree adjustment screws can have two regions with different threadpitches to produce a reduced apparent thread pitch.

In yet another embodiment, the pedestal assembly positioning systemfurther includes a bellows to maintain a pressure difference between theinside and outside of the processing system while adjusting theadjustment screws.

In yet another embodiment, the pedestal assembly positioning systemfurther includes a locking mechanism. The locking mechanism can includefour locking screws.

In another embodiment, a substrate processing system includes aprocessing chamber, a pedestal, an optical measurement assembly, alateral adjustment assembly and a vertical adjustment assembly. Theprocessing chamber includes a fixed reference object located inside theprocessing chamber. A portion of the processing chamber is transparent.The pedestal for supporting a work piece can be located within theprocessing chamber. The optical measurement assembly is coupled to theexterior of the processing chamber. The optical measurement assemblymeasures the location and tilt of the pedestal by transmitting lightinto the chamber through the transparent portion of the chamber anddetecting reflected light after the reflected light leaves the chamberthrough the transparent portion of the chamber. The fixed referenceobject inside the processing chamber and a portion of the pedestal arepositioned so that they can be exposed to light from outside of theprocessing chamber through the transparent portion of the chamber. Thelateral adjustment assembly can adjust the lateral location of thepedestal relative to the fixed reference object and the verticaladjustment assembly can adjust the height and tilt of the pedestalrelative to the fixed reference object. The lateral adjustment assemblyand the vertical adjustment assembly are outside of the processingchamber and are coupled to the pedestal through a pedestal shaft that iscoupled to the processing chamber through a bellows.

In yet another embodiment, the portion of the processing chamber that istransparent is a quartz dome or a view port.

In yet another embodiment, the fixed reference object in the processingchamber is an outer ring rigidly attached to the processing chamber.

In yet another embodiment, the pedestal further includes an inner ringthat is rigidly attached to the pedestal and is nearly concentric withthe outer ring.

In yet another embodiment, the pedestal used in the substrate processingsystem is a susceptor.

In yet another embodiment, the lateral adjustment assembly used in thesubstrate processing system includes three adjustment screws nearlyequally spaced around the outer ring. The bellows can maintain apressure difference between the inside and outside of the substrateprocessing system while adjusting the adjustment screws.

In yet another embodiment, the substrate processing system furtherincludes a locking mechanism for securing the pedestal in place. Thelocking mechanism can include four locking screws.

In yet another embodiment, a method of adjusting a position of apedestal assembly includes measuring the tilt and location of thepedestal relative to a processing system reference, leveling thepedestal in response to the tilt measurement to reduce the tilt of thepedestal relative to the processing system reference, translating thepedestal to be at a predetermined location in response to the locationmeasurement without significantly affecting the tilt. The processingsystem reference is rigidly attached to a processing system and can be apreheat ring. The pedestal can be a susceptor.

In yet another embodiment, the step of leveling is done before the stepof translating.

In yet another embodiment, the method of adjusting a position of apedestal further includes adjusting the height of the pedestal to apredetermined level without significantly affecting the tilt.

In yet another embodiment, the step of measuring the location of thepedestal further includes reflecting light from a plurality of locationsaround the pedestal and the processing system reference and analyzingthe reflected light to determine an indication of location of thepedestal relative to the processing system reference at the plurality oflocations. The indication of location can be a difference in heightbetween the pedestal and the processing system reference. Alternatively,the indication of location can be a separation between an outer edge ofthe pedestal and an inner edge of the processing system reference.

In yet another embodiment, reflecting light from a plurality oflocations includes reflecting light from at least two locations todetermine whether the pedestal is centered within the processing systemreference.

In yet another embodiment, reflecting light from a plurality oflocations includes reflecting light from at least three locations todetermine the height and lateral location of the pedestal.

In yet another embodiment, reflecting light from a plurality oflocations includes reflecting light from at least three locations todetermine the tilt of the pedestal.

In yet another embodiment, analyzing the reflected light furtherincludes calculating the tilt angle from a height difference between thetwo markers.

In yet another embodiment, the step of leveling the pedestal to reducethe tilt of the pedestal further includes adjusting the tilt of thepedestal so that the angle between a surface on the pedestal and theprocessing system reference is less than or equal to 0.15 degrees.

In yet another embodiment, the step of positioning the pedestal furtherincludes maintaining the angle between a surface on the pedestal and theprocessing system reference to be less than or equal to 0.15 degrees,adjusting the horizontal location of the pedestal to be within 0.5 mm ofthe predetermined location, verifying that the angle between a surfaceon the pedestal and the processing system reference is less than orequal to 0.15 degrees after the adjustment, and securing the position ofthe pedestal by locking the pedestal into place.

In yet another embodiment, the step of positioning the pedestal furtherincludes maintaining the angle between a surface on the pedestal and theprocessing system reference to be less than or equal to 0.15 degrees,adjusting the horizontal location of the pedestal to be within 0.5 mm ofthe predetermined location, adjusting the height of the pedestal to bewithin 0.3 mm of the predetermined location, verifying that the anglebetween a surface on the pedestal and the processing system reference isless than or equal to 0.15 degrees after the adjustments, and securingthe position of the pedestal by locking the pedestal into place.

In yet another embodiment, the method of adjusting a position of apedestal further includes checking the level and location of thepedestal while rotating the pedestal. Checking the level and location ofthe pedestal while rotating the pedestal can include checking that theangle between a surface on the pedestal and the processing systemreference is less than or equal to 0.5 degrees and that the horizontallocation of the pedestal is within 1.0 mm of the predetermined location.

In yet another embodiment, a method of processing a substrate in asubstrate processing system includes pumping a process chamber with apedestal inside to a pressure less than 80 torr, measuring the tilt andlocation of the pedestal relative to a processing system reference,leveling the pedestal in response to the tilt measurement to reduce thetilt of the pedestal relative to the processing system reference, andtranslating the pedestal to be at a predetermined location in responseto the location measurement without significantly affecting the tilt.The processing system reference can be rigidly attached to the substrateprocessing system.

In yet another embodiment, the method of processing a substrate in asubstrate processing system further includes checking the level andlocation of the pedestal while rotating the pedestal. Checking the leveland location of the pedestal while rotating the pedestal can includechecking that the angle between a surface on the pedestal and theprocessing system reference is less than or equal to 0.5 degrees andthat the horizontal location of the pedestal is within 1.0 mm of thepredetermined location.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the inventionmay be realized by reference to the remaining portions of thespecification and the drawings, presented below. The Figures areincorporated into the detailed description portion of the invention.

FIG. 1A is a schematic view of a prior art pedestal assembly depicting atilted pedestal;

FIG. 1B is a schematic view of a prior art pedestal assembly depicting apedestal whose tilt has been removed;

FIG. 2A is a perspective view of an optical measurement assemblypositioned above a processing chamber according to an embodiment of theinvention;

FIG. 2B is a height profile determined with an optical measurementassembly according to an embodiment of the invention;

FIG. 3 is a view of a substrate processing system with a non-contactposition sensing system and a positioning assembly according to anembodiment of the invention;

FIG. 4A is a perspective view of a positioning assembly according to anembodiment of the invention;

FIG. 4B is a cross-sectional view of a positioning assembly according toan embodiment of the invention;

FIG. 4C is a schematic view of a portion of a positioning assemblyaccording to an embodiment of the invention;

FIG. 4D is a schematic view of a portion of a positioning assemblyaccording to an embodiment of the invention;

FIG. 4E is a schematic view of a portion of a positioning assemblyaccording to an embodiment of the invention;

FIG. 4F is a schematic view of a portion of a positioning assemblyaccording to an embodiment of the invention;

FIG. 5A is a cross-sectional view of a substrate processing systemaccording to an embodiment of the invention;

FIG. 5B is a top view of a portion of a substrate processing systemaccording to an embodiment of the invention; and

FIG. 6 is a flowchart showing the steps used to process a substrate in asubstrate processing system where the pedestal has been positionedaccording to an embodiment of the invention.

DETAILED DESCRIPTION

Aspects of embodiments disclosed herein are used to improve theperformance of substrate processing systems by improving uniformity andrepeatability of the process running on the substrate processing system.The uniformity and repeatability of processes are impacted by thelocation and levelness of the pedestal supporting the substrate beingprocessed. Embodiments of the present invention relate to measuring thepedestal and/or substrate tilt and location relative to a fixedreference and adjusting the tilt and location of the pedestal and/orsubstrate. Measurements are performed using a non-contact and in-situmethods to precisely measure the pedestal and/or substrate tilt andlocation. This measurement is used as a feedback for either manualadjustment or automatic closed-loop servo based adjustment of the tiltand translation mechanism until the pedestal is level, centered andadjusted for height. The non-contact method allows the measurement to bedone in vacuum thus reducing the need for the chamber to be open andvented significantly minimizing any down-time and recovery time. Afeature of disclosed embodiments involves the capability of decouplingthe adjustment of the tilt of a pedestal and its lateral location in theXY plane. Another feature of disclosed embodiments involves thecapability of making adjustments while a substrate processing system isfully assembled and possibly under vacuum.

Properties of disclosed embodiments will often be described herein withparticular relevance to high temperature substrate processing systemswhich possess a known acute need for benefits of the disclosedembodiments. However, other processing equipment in use now and thosenot yet developed may also benefit from the disclosed embodiments aswell.

An exemplary process and associated process chamber will be used as avehicle to disclose embodiments in this disclosure. The exemplaryprocess is epitaxial film growth (a.k.a. EPI) and is known to be proneto irreproducibility of pedestal and substrate position. Theirreproducibility can be found when matching a process from one systemto another or when qualifying a process after any procedure whichnecessitates reassembly. Particular aspects of the film which may varybased on substrate placement include (but are not limited to) filmthickness, impurity/dopant density and crystal defectivity. Variation ofthese fundamental aspects can result in changes in other thin filmmetrics like electrical, magnetic and physical characterizations. Thesevariations can be between a first wafer and a second wafer, eachprocessed at different positions and/or within a wafer which could becaused by a tilted or poorly centered wafer.

A reference object within a process chamber should be defined in orderto measure the height, lateral placement (also referred to herein ascentrality), and tilt of a pedestal or substrate. This may be a gasdistribution plate above a wafer in a plasma chemical vapor depositionprocess or a target in a physical vapor deposition process or areference ring. In an EPI process the tilt and height are measuredrelative to a reference ring which is a preheat ring like the onesdescribed in FIGS. 1A and 1B. A silicon-containing gas is flowed overthe preheat ring and over the substrate where deposition occurs. EPIprocessing chambers, like some other processing chambers, rotate acircular substrate (also called a wafer) during deposition to improveuniformity. Substrates can include glass, ceramics, metals or other workpieces including wafers.

Preheating the gas in this way can, for example, increase the depositionrate near the edge of a wafer. If the preheat ring is held at too low atemperature or the height of the preheat ring is too high in comparisonwith the deposition surface of the wafer, the silicon film grown on thesubstrate may have a reduced thickness near the edge. When depositing ona wafer that is rotated during deposition, these effects can result inan undesirably large edge exclusion (greater than two or threemillimeters). In other words, the chips formed near the edge of thewafer would not have optimized properties or may not function. Even ifthe height is correct and there is no tilt, a lateral placement error ofthe wafer in the plane of the preheat ring will create a variation inthe gap 120,121 between the preheat ring 116 and the wafer pedestal 112.Rotating the wafer during deposition may create a rotationally symmetricdeposition, but the uniformity of the film, especially near the edge,may still be impacted.

FIG. 2A illustrates an EPI processing system 200 having a quartz domewith an optical measurement assembly used to measure the location andtilt of a work piece, or other component, located within the EPIprocessing system 200, in accordance with an embodiment of theinvention. The EPI processing system 200 includes a pedestal 204, and apreheat ring 206 that is separated from the pedestal 204 by a gap 210.The pedestal 204 can be a susceptor or wafer supporting structure. Theoptical measurement assembly includes a laser gauge 218 which is used tosupply and detect light that reflects from the pedestal 204, preheatring 206, wafer (not shown) or other components located within the EPIprocessing system 200. Optical measurements of the pedestal 204, preheatring 206, wafer (not shown) or other components located within the EPIprocessing system 200 are made by shining light from the laser gauge 218through the quartz dome. With these measurements, relative positionsbetween the components, such as the location of the wafer relative tothe preheat ring, can be determined. During operation, a sheet of lightis reflected from the pedestal 204 and the preheat ring 206, while someof the light enters the gap between the two 210. Although the lightsource used in this embodiment is a laser, those skilled in the art willrecognize that the light source can be any source that produces acollimated light. In this embodiment, measurements are performed on thepedestal 204, preheat ring 206, wafer (not shown) or other componentslocated within the EPI processing system 200, while the EPI processingsystem 200 is fully assembled and is under vacuum or at the processingpressure. The quartz dome, which is located between the laser gauge 218and the two reflecting surfaces (the pedestal 204 and the preheat ring206), allows light to pass through so that optical measurements can bedone on components located within the EPI processing system 200.

In order to better understand and appreciate disclosed embodiments,reference is now made to FIG. 2B, which is a linear distribution ofheight measurements 202 including the height of the pedestal 204 and thepreheat ring 206 at one location along the circumference of the pedestal204. The sequence of height measurements can be used to calculate aheight difference 224 between the pedestal and the preheat ring. Thesequence can also be used to calculate the gap 228 between the outersurface of the pedestal and the inner surface of the preheat ring. Avariety of optical measurement assemblies can be used to produce theheight and/or gap measurements of FIG. 2B, including illuminating theline of measurement sites from an angle and measuring the location ofthe specularly reflected light with a two dimension optical detector.

The measurement represented in FIG. 2B can be repeated around thepedestal at three or more locations around the circumference of thepedestal in order to calculate the pedestal height, tilt (magnitude anddirection) and centrality (magnitude and direction). Measurements arerepeated and adjustments are made until the height difference 224 atthree or more different locations around the pedestal are within apredetermined tolerance and the average of the three height differencesis substantially close to a predetermined value. The height can becorrected with a linear vertical translation generated manually or witha motor.

The three measurements can be made by placing three or more opticalmeasurement assemblies around the circumference of the chamber in someembodiments, thereby enabling the measurements to be madesimultaneously. In alternative embodiments, fewer optical measurementassemblies can be used and some can be relocated between measurements tosecure enough measurement sites. An optical measurement assembly may bemounted on a translation stage, enabling measurements to be made atdifferent locations within the processing chamber without humanintervention. FIG. 3 shows a cross-section of an optical measurementassembly 318 mounted on a guide rail 331 which guides the opticalmeasurement assembly 318 during translation. In embodiments, the guiderail 331 may be curved so the optical measurement assembly 318 (movingabove the quartz dome 314) may be positioned to make measurements atmultiple locations around the edges of the susceptor 304 and preheatring 306. In still further embodiments, a support arm moves the opticalmeasurement assembly 318 without requiring a guide rail, adjustingposition with two axes of motion allowing flexibility in placement ofthe assembly. The optical measurement assembly 318 may, alternatively,be moved on a rotary hinge so the position of the assembly is adjustablearound the edges of the susceptor 304and preheat ring 306 in a mannersimilar to the curved guide rail 331. Use of a rotary hinge and/or aguide rail reduce the degrees of freedom in the motion of the opticalmeasurement assembly 318 which improves the accuracy and repeatabilityof the placement of the measurement assembly 318. Accurate andrepeatable placement is important for some of measurement techniquesdescribed below.

Processing chambers which do not have quartz domes can also be used inalternative embodiments. Viewports with diameters sufficiently large tomake one or more measurements need to be installed on the processingchamber. For example, three quartz viewports may be positioned on thetop of a processing chamber with an angular separation of about 120° toenable three measurements to guide tilt and centrality adjustments.Different essentially transparent viewports may also be used employingalternative transparent materials; different angular separations arepresent in some disclosed embodiments.

In an alternative optical measurement assemblies, two light beams arefocused down and reflected, one from the pedestal and one from thepreheat ring, and each then directed towards one or more CCD or CMOSarray detector(s). The detector(s) can be one or two dimensional and is(are) used to determine or infer the sizes of the reflected beam at thedetector. These sizes can then be assigned a height value and the heightcan be calculated with an analytic approximation or retrieved from alook-up table. This measurement procedure can also be done, inembodiments, by reflecting two collimated beams from the pedestal andpreheat ring and determining the size of the reflected beam as above.This method is called optical triangulation and relies on properties ofthe two surfaces, which are characterized before a measurement, to widenthe beam at a precharacterized rate.

A variety of other more involved optical techniques may be used as well.In some embodiments, the techniques may rely on interferometry, thephase shift method or other time-of-flight techniques. Additionally,acoustic sources and sensors can be used in a variety ways, employingsome of the same principles described previously with respect to opticalmethods. In this case, the measurements should be made through anacoustically transmissive material such as the quartz domes often usedin EPI reactors. Signal processing techniques may be needed to suppressbackground signal and accentuate the sound returning from the susceptoror preheat ring. The background signal may include contributions from areflections occurring at other material interfaces (e.g. air-quartz) butmay also arise from the large spot sizes often needed for acousticmethods.

The advantages of measuring and adjusting the height, tilt andcentrality of the pedestal originate from the sensitivity of the processto the position of the wafer and the high probability that the positionof the wafer will vary with the position of the pedestal. As such,disclosed optical measurement assemblies can be used to make themeasurements with the wafer in place instead of measuring the positionof the pedestal. This can result in additional useful information sincethe measurement is being made at the deposition surface.

At least three spatially separated measurements are needed for adetermination of height or tilt. Since the outer diameter of thepedestal and the inner diameter of the preheat ring are known, twomeasurements are sufficient to determine the lateral location orcentrality of the pedestal. In one disclosed embodiment, tilt isadjusted first, followed by the height and then the centrality. Inanother embodiment, height is adjusted first, followed by the tilt andthen the centrality. Although other orders are possible, in thepreferred embodiment the tilt should be adjusted before the centralitysince the tilt adjustment can affect centrality. The centralityadjustment, using the methods discussed herein, can be done withoutaffecting the tilt. During the adjustment of the centrality,measurements can be repeated and adjustments made until the gap 228 atmultiple locations are within a specific tolerance of a predeterminedgap.

Adjusting the gap may be done in a way that does not significantlyaffect the tilt. In order to realize such an independence, separatemechanisms are employed for leveling the substrate support assembly andfor translating the substrate support assembly. Leveling the substratesupport assembly adjusts the tilt of the substrate support assembly sothat it is level with respect to a reference. Translating the substratesupport assembly moves the substrate support assembly so that it may becentered both horizontally and vertically with respect to a reference.FIG. 3 is a side view of the substrate processing system with a pedestal304 and a positioning assembly 308. The positioning assembly 308includes both a vertical adjustment assembly portion and a lateraladjustment assembly portion. The vertical adjustment assembly portionincludes vertical screws 312 for height and tilt adjustments while thelateral adjustment assembly portion includes horizontal screws 316 toadjust the lateral placement (centrality). Tilting the pedestal 304 withthe vertical screws can affect the lateral placement (centrality) of thepedestal 304. In other words, adjusting the tilt of the pedestal 304 cancause changes in the lateral placement (centrality) of the pedestal 304.The horizontal screws 316 of the positioning assembly 308 are used tocorrect the centrality of the pedestal 304 without significantlyaffecting the tilt of the pedestal 304.

FIGS. 4A and 4B are views of the positioning assembly 308, which isdiscussed above with reference to FIG. 3. FIG. 4A is a perspective viewthe positioning assembly 308 including three lateral adjustment screws404 (two shown), a bellows 431, three vertical adjustment screws 443(two shown). One of the three screws 443 may be a post if height is tobe adjusted with a separate assembly. FIG. 4B is a cross-sectional viewof the positioning assembly 308 including the three lateral adjustmentscrews 404 (one shown), an outer stationary ring 409, a first stationaryflange 411, a second stationary flange 413, an adjustable support ring419, a first mobile flange 421, a second mobile flange 423, a bellows431, and the three vertical adjustment screws 443 (one shown). Thepositioning adjustments of the pedestal 304 are made by the positioningassembly 308. The lateral location of the shaft and pedestal may beadjusted using three lateral adjustment screws 404, such that the gapbetween the pedestal and preheat ring, discussed above with reference toFIG. 2, is uniform all around the circumference. In an embodiment, each404 of the three lateral adjustment screws are separated by 120°. Thetilt of the pedestal remains essentially unaffected during theadjustment of the lateral adjustment screws 404. This is made possiblebecause the lateral adjustment screws 404 apply forces to an adjustablesupport ring 419 relative to an outer stationary ring 409. The outerstationary ring is rigidly coupled to the stationary flanges (411, 413)and the outer portion of the processing chamber. Therefore theadjustable support ring 419 can be moved laterally along with mobileflanges (421, 423) and components below these two flanges. Since theadjustment of the lateral adjustment screws 404 move the componentsbelow the adjustable support ring 419 en masse, and the substratesupport assembly is attached at the bottom of its support shaft, theorientation of the shaft is maintained and no tilt is imparted. Enablingthis motion is the bellows 431, which flexes as adjustments are made.The presence of a bellows 431 also enables the processing chamber to bemaintained at a pressure different from atmospheric pressure even duringthe adjustment.

The lateral adjustment screws 404 can be turned to cause lateraldisplacement of the pedestal 304 using different embodiments ofoperation as illustrated in FIGS. 4C-4F.

FIG. 4C illustrates an embodiment where lateral adjustment screws 404are used to push the adjustable support ring 419 locally away from theouter stationary ring 409. Before the adjustable support ring 419 can bemoved by a first screw, the complementary screws of the positioningassembly may be unscrewed or “backed off” to allow the necessary amountof motion by the adjustable support ring 419. After backing them off,the first screw can be used to push the adjustable support ring 419 inthe preferred direction. In disclosed embodiments, there are one or moreof other screws, called set screws, which are screwed in to hold thesubstrate support assembly in place once the pedestal is in the properlocation. There may be one, two, three, four or more set screws indifferent disclosed embodiments.

FIG. 4D illustrates another embodiment where the lateral adjustmentscrews 404 pull the adjustable support ring 419 toward the outerstationary ring 409. In the embodiment shown, turning the screwclockwise for right-handed threads results in a decrease in theseparation of the adjustable support ring 419 and the outer stationaryring 409. Analogously to the pushing configuration of FIG. 4C, thecomplementary screws of the positioning assembly may be unscrewed or“backed off” to allow the necessary amount of motion by the adjustablesupport ring 419.

The ability to fine-tune the centrality of the pedestal with the twoembodiments represented by FIGS. 4C and 4D is determined, in part, bythe thread pitch of the bolts and threaded holes. Creating a tighterthread pitch to increase the ability to control the lateral location ofthe pedestal introduces a higher risk of damaging the threads duringtuning operations. To address this issue, an additional mode ofoperating the screws is disclosed with reference to FIGS. 4E and 4F butcan be implemented in a variety of analogous designs with similarfunctions.

FIG. 4E illustrates an embodiment where the lateral adjustment screws404 have two regions with different thread pitches. A coarser thread 425may be used for the mating surfaces between lateral adjustment screws404 and the outer stationary ring 409, while a finer thread pitch 433 isused for the mating surfaces of the lateral adjustment screws 404 andthe adjustable support ring 419. The net effect is that the apparentthread pitch can be reduced (i.e. made smaller or finer) than eitherindividual pitch.

FIG. 4F illustrates another embodiment where a similar effect iscreated. The lateral adjustment screws 404 may have a bored out interiorwith a given thread pitch to mate with a threaded rod rigidly attachedto the adjustable support ring 419. The lateral adjustment screws 404may have a different thread pitch (shown as coarser threads 425 in FIG.4F) on the outer surface for mating with the outer stationary ring 409from the inner thread pitch (shown as finer threads 433) for mating withthe adjustable support ring 419. Again, the net effect is that theapparent thread pitch can be finer than either individual pitch.

In any of the disclosed embodiments involving coarse and fine threads,the more similar the coarse and fine thread pitches are to one another,the finer the apparent thread pitch becomes. In the following examples,reference will be made to a thread density which is defined as themultiplicative inverse of the thread pitch. The thread pitch may bemeasured in inches per thread whereas the thread density may be measuredin threads per inch. Thread density is commonly available in screw andbolt charts known to those of skill in the art. In some disclosedembodiments, the thread densities are 32 and 24 threads per inch whichresult in an apparent thread density of about 96 threads per inch. Inother disclosed embodiments, the thread densities are 32 and 28 threadsper inch which result in an apparent thread density of 224 threads perinch. Threads with 96 or 224 threads per inch would be more expensive tomanufacture and probably not be strong enough to supply a useful forcewithout the risk of galling.

The adjustments which are made with the tilt mechanisms and the screwsdisclosed in FIGS. 4A-4F and the associated discussion can be rotatedmanually during a continuous measurement made by the optical measurementassemblies disclosed earlier. In alternative embodiments, a discretemeasurement can be made followed by an adjustment of the tilt and/or thelateral adjustment screws. This may then be followed by anothermeasurement and adjustment as necessary. In another disclosedembodiment, the tilt and location adjustments are done automaticallywith feedback from the optical measurement assembly. A fully automaticclosed-loop servo based adjustment of the height, tilt and/or lateraladjustment mechanisms is present in disclosed embodiments.

The vertical adjustment screws 443 and supports illustrated in FIGS.4A-B are mechanisms for adjusting tilt and height. The upper bellows 431accommodates the motion relating to adjustments of height, tilt andcentrality of the pedestal assembly. For example, when the pedestal israised relative to the preheat ring, the upper bellows 431 willcompress. In addition to the adjustment of the vertical adjustmentscrews 443, height adjustments can also be made, in embodiments, with aseparate motorized lift assembly.

Herein, the use of the terms “light”, “optical” and “optics” does notcarry any implication that the electromagnetic radiation involved mustbe from the visible portion of the spectrum. The light can be of anywavelength. Also herein, the use of the terms “reflecting” and“reflected” to describe the light which has illuminated the pedestal,substrate or preheat ring, does not carry any implication that the lightis only reflected. The light may be scattered from a rough surface orexhibit an interference effect so that the angle of incidence does notequal the angle of departure.

Exemplary Systems

FIGS. 5A-B shows an example of a substrate processing system accordingto embodiments of the invention. The processing apparatus 510 shown inFIG. 5A is a deposition reactor and includes a deposition chamber 512having an upper dome 514, a lower dome 516 and a sidewall 518 betweenthe upper and lower domes 514 and 516. Cooling fluid (not shown) may becirculated through sidewall 518 to cool o-rings used to seal domes 514and 516 against sidewall 518. An upper liner 582 and a lower liner 584are mounted against the inside surface of sidewall 518. The upper andlower domes 514 and 516 are made of a transparent material to allowheating light to pass through into the deposition chamber 512.

Within the chamber 512 is a flat, circular pedestal 520 for supporting awafer in a horizontal position. The pedestal 520 can be a susceptor orother wafer supporting structure and extends transversely across thechamber 512 at the sidewall 518 to divide the chamber 512 into an upperportion 522 above the pedestal 520 and a lower portion 524 below thepedestal 520. The pedestal 520 is mounted on a shaft 526 which extendsperpendicularly downward from the center of the bottom of the pedestal520. The shaft 526 is connected to a motor (not shown) which rotatesshaft 526 and thereby rotates the pedestal 520. An annular preheat ring528 is connected at its outer periphery to the inside periphery of lowerliner 584 and extends around the pedestal 520. The preheat ring 528occupies nearly the same plane as the pedestal 520 with the inner edgeof the preheat ring 528 separated by a gap from the outer edge of thepedestal 520.

An inlet manifold 530 is positioned in the side wall 518 of chamber 512and is adapted to admit gas from a source of gas or gases, such as tanks141 a-c, into the chamber 512. The flow of gases from bottles 141 a-care preferably independently controlled with manual valves and computercontrolled flow controllers 142 a-c. An outlet port 532 is positioned inthe side of chamber 512 diametrically opposite the inlet manifold 530and is adapted to exhaust gases from the deposition chamber 512.

A plurality of high intensity lamps 534 are mounted around the chamber512 and direct their light through the upper and lower domes 514, 516onto the pedestal 520 (and preheat ring 528) to heat the pedestal 520(and preheat ring 528). Pedestal 520 and preheat ring 528 are made of amaterial, such as silicon carbide, coated graphite which is opaque tothe radiation emitted from lamps 534 so that they can be heated byradiation from lamps 534. The upper and lower domes 514, 516 are made ofa material which is transparent to the light from the lamps 534, such asclear quartz. The upper and lower domes 514, 516 are generally made ofquartz because quartz is transparent to light of both visible and IRfrequencies; it exhibits a relatively high structural strength; and itis chemically stable in the process environment of the depositionchamber 512. Although lamps are the preferred means for heating wafersin deposition chamber 512, other methods may be used such as resistanceheaters and RF inductive heaters. An infrared temperature sensor 536such as a pyrometer is mounted below the lower dome 516 and faces thebottom surface of the pedestal 520 through the lower dome 516. Thetemperature sensor 536, is used to monitor the temperature of thepedestal 520 by receiving infra-red radiation emitted from the pedestal520. A temperature sensor 537 for measuring the temperature of a wafermay also be present in some disclosed embodiments.

An upper clamping ring 548 extends around the periphery of the outersurface of the upper dome 514. A lower clamping ring 550 extends aroundthe periphery of the outer surface of the lower dome 516. The upper andlower clamping rings 548 and 550 are secured together so as to clamp theupper and lower domes 514 and 516 to the side wall 518.

Reactor 510 includes a gas inlet manifold 530 for feeding process gasesinto chamber 512. Gas inlet manifold 530 includes a connector cap 538, abaffle 574, an insert plate 579 positioned within sidewall 518, and apassage 560 formed between upper liner 582 and lower liner 584. Passage560 is connected to the upper portion 522 of chamber 512. Process gasfrom gas cap 538 passes through baffle 574, insert plate 579 and passage560 and into the upper portion 522 of chamber 512.

Reactor 510 also includes an independent inert gas inlet 562 for feedingan inert purge gas, such as but not limited to, hydrogen (H₂) andnitrogen (N₂), into the lower portion 524 of deposition chamber 512. Asshown in FIG. 5A, inert purge gas inlet 562 can be integrated into gasinlet manifold 530, if preferred, as long as a physically separate anddistinct passage 562 through baffle 574, insert plate 579, and lowerliner 584 is provided for the inert gas, so that the inert purge gas canbe controlled and directed independent of the process gas. Inert purgegas inlet 562 need not necessarily be integrated or positioned alongwith gas inlet manifold 530, and can for example be positioned onreactor 510 at an angle of 90° from deposition gas inlet manifold 530.

Reactor 510 also includes a gas outlet 532. The gas outlet 532 includesan exhaust passage 590 which extends from the upper chamber portion 522to the outside diameter of sidewall 518. Exhaust passage 590 includes anupper passage 592 formed between upper liner 582 and lower liner 584 andwhich extends between the upper chamber portion 522 and the innerdiameter of sidewall 518. Additionally, exhaust passage 590 includes anexhaust channel 594 formed within insert plate 579 positioned withinsidewall 518. A vacuum source, such as a pump (not shown) for removingmaterial from chamber 512 is coupled to exhaust channel 594 on theexterior of sidewall 518 by an outlet pipe 533. Thus, process gas fedinto the upper chamber portion 522 is exhausted through the upperpassage 592, through exhaust channel 594 and into outlet pipe 533.

The single wafer reactor shown in FIG. 5A is a “cold wall” reactor. Thatis, sidewall 518 and upper and lower liners 582 and 584, respectively,are at a substantially lower temperature than preheat ring 528 andpedestal 520 (and a wafer placed thereon) during processing. Forexample, in a process to deposit an epitaxial silicon film on a wafer,the pedestal and wafer are heated to a temperature of between 550-1200°C., while the sidewall (and liners) are at a temperature of about400-600° C. The sidewall and liners are at a cooler temperature becausethey do not receive direct irradiation from lamps 534 due to reflectors535, and because cooling fluid is circulated through sidewall 518.

Gas outlet 532 also includes a vent 596 which extends from the lowerchamber portion 524 through lower liner 584 to exhaust passage 590. Vent596 preferably intersects the upper passage 592 of exhaust passage 590as shown in FIG. 5A. Inert purge gas is exhausted from the lower chamberportion 524 through vent 596, through a portion of upper chamber passage592, through exhaust channel 594, and into outlet pipe 533. Vent 596allows for the direct exhausting of purge gas from the lower chamberportion to exhaust passage 590.

According to the present invention, process gas or gases 598 are fedinto the upper chamber portion 522 from gas inlet manifold 530. Aprocess gas, according to the present invention, is defined as a gas orgas mixture which acts to remove, treat, or deposit a film on a wafer ora substrate placed in chamber 512. According to the present invention, aprocess gas comprising HCl and an inert gas, such as H₂, is used totreat a silicon surface by removing and smoothing the silicon surface.In an embodiment of the present invention a process gas is used todeposit a silicon epitaxial layer on a silicon surface of a wafer placedon pedestal 520 after the silicon surface has been treated. Process gas598 generally includes a silicon source, such as but not limited to,monosilane, trichlorosilane, dichlorosilane, and tetrachlorosilane,methyl-silane, and a dopant gas source, such as but not limited tophosphine, diborane, germaine, and arsine, among others, as well asother process gases such as oxygen, methane, ammonia, etc. A carriergas, such as H₂, is generally included in the deposition gas stream. Fora process chamber with a volume of approximately 5 liters, a depositionprocess gas stream between 35-75 SLM (including carrier gas) istypically fed into the upper chamber portion 522 to deposit a layer ofsilicon on a wafer. The flow of process gas 598 is essentially a laminarflow from inlet passage 560, across preheat ring 528, across pedestal520 (and wafer), across the opposite side of preheat ring 528, and outexhaust passage 590. The process gas is heated to a deposition orprocess temperature by preheat ring 528, pedestal 520, and the waferbeing processed. In a process to deposit an epitaxial silicon layer on awafer, the pedestal 520 and preheat ring 528 are heated to a temperatureof between 800° C.-1200° C. A silicon epitaxial film can be formed attemperatures as low as 550° C. with silane by using a reduced depositionpressure.

Additionally, while process gas is fed into the upper chamber portion,an inert purge gas or gases 599 are fed independently into the lowerchamber portion 524. An inert purge gas is defined as a gas which issubstantially unreactive at process temperatures with chamber featuresand wafers placed in deposition chamber 512. The inert purge gas isheated by preheat ring 528 and pedestal 520 to essentially the sametemperature as the process gas while in chamber 512. Inert purge gas 599is fed into the lower chamber portion 524 at a rate which develops apositive pressure within lower chamber portion 524 with respect to theprocess gas pressure in the upper chamber portion 522. Process gas 598is therefore prevented from seeping down through gap and into the lowerchamber portion 524, and depositing on the backside of pedestal 520.

FIG. 5B shows a portion of the gas inlet manifold 530 which supplies gasto the upper zone of the processing chamber. The insert plate 579 ofFIG. 5B is shown to be constituted by an inner zone 128 and an outerzone 130. According to this embodiment of the invention the compositionof the process gas which flows into inner zone 128 can be controlledindependently of the composition of the gas which flows into outer zone130. In addition, the flow rate of the gas to either of the two halves128 a, 128 b of the inner zone 128 can be further controlledindependently from one another. This provides two degrees of control forthe gas flow for the purposes of controlling the composition of theprocess gas mix over different zones of the semiconductor wafer.

Processing apparatus 510 shown in FIG. 5A includes a system controller150 which controls various operations of apparatus 510 such ascontrolling gas flows, substrate temperature, and chamber pressure. Inan embodiment of the present invention the system controller 150includes a hard disk drive (memory 152), a floppy disk drive and aprocessor 154. The processor contains a single board computer (SBC),analog and digital input/output boards, interface boards and steppermotor controller board. Various parts of processing apparatus 510 canconform to the Versa Modular Europeans (VME) standard which definesboard, card cage, and connector dimensions and types. The VME standardalso defines the bus structure having a 16-bit data bus and 24-bitaddress bus.

System controller 150 controls all of the activities of the apparatus510. The system controller executes system control software, which is acomputer program stored in a computer-readable medium such as a memory152. Memory 152 may be a hard disk drive, but memory 152 may also beother kinds of memory. Memory 152 may also be a combination of one ormore of these kinds of memory. The computer program includes sets ofinstructions that dictate the timing, mixture of gases, chamberpressure, chamber temperature, lamp power levels, pedestal position, andother parameters of a particular process. Of course, other computerprograms such as one stored on another memory device including, forexample, a floppy disk or another appropriate drive, may also be used tooperate system controller 150. An input/output device 156 such as an LCDmonitor and a keyboard is used to interface between a user and systemcontroller 150.

FIG. 6 is a flowchart showing the a sequence of steps which may be usedto level and adjust the location of a pedestal in a substrate processingsystem according to an embodiment of the invention. The process startsin 600 where the substrate processing system is prepared for processing.This can occur after the substrate processing system has been servicedor at fixed intervals where calibration of the system is normally done.In step 605, the substrate processing system is pumped down to apressure where further pumping will not causes sufficient forces to movecomponents within the substrate processing system. In one embodiment thesubstrate processing system is pumped down, with a pedestal inside, to apressure less than 80 torr. Next in step 610, the tilt and location ofthe pedestal relative to a processing system reference are measured. Thetilt and location are measured using the non-contact optical measurementassembly discussed above with reference to FIGS. 2A-2C.

In step 615, the pedestal is leveled in response to the tilt measurementto reduce the tilt of the pedestal relative to the processing systemreference. In step 620, the height of the pedestal is adjusted relativeto the processing system reference. In step 625, the lateral location ofthe pedestal is adjusted to be at a predetermined lateral location inresponse to the location measurement without significantly affecting thetilt. The predetermined location can be a distance away from one or morereference points or a distance away from an object. In one embodimentthe predetermined location is centering an inner ring located on thepedestal with respect to an outer ring located on the substrateprocessing system so that the inner ring on the pedestal lies within andconcentric to the outer ring (ie. the inner ring is centered withrespect to the outer ring). Next in step 630, the tilt and location ofthe pedestal relative to a processing system reference are measuredagain, as was done in step 610. In step 635, a decision is made whetherthe location and tilt of the pedestal is within acceptable tolerances.If the decision is that the measurements are within acceptabletolerances the process continues to step 640 where the setup of thepedestal ends and the substrate processing system can be used to processwafers. If the decision is that the measurements are not withinacceptable tolerances then the process goes to step 615 and continues tostep 635 leveling and adjusting the pedestal.

The process for measuring and adjusting positions in accordance with thepresent invention can be implemented using a computer program productwhich is stored in memory 152 and is executed by processor 154. Thecomputer program code can be written in any computer readableprogramming language, such as, assembly language, C, C++, Pascal,Fortran, or others. Suitable program code is entered into a single file,or multiple files, using a program editor, and stored or embodied in acomputer usable medium, such as a memory system of the computer. Whenthe edited code is in a high level language, the code may be compiled,and the resultant compiled code is then linked with an object code ofprecompiled library routines. To execute the linked compiled objectcode, the system user invokes the object code, causing the computersystem to load the code in memory, from which the CPU reads and executesthe code to perform the tasks identified in the program. Also stored inmemory 152 are process parameters such as process gas flow rates (e.g.,H₂ and HCl flow rates), process temperatures and process pressurenecessary to make measurements and adjustments in accordance with thepresent invention.

It will also be recognized by those skilled in the art that, while theinvention has been described above in terms of preferred embodiments, itis not limited thereto. Various features and aspects of theabove-described invention may be used individually or jointly. Further,although the invention has been described in the context of itsimplementation in a particular environment and for particularapplications, those skilled in the art will recognize that itsusefulness is not limited thereto and that the present invention can beutilized in any number of environments and implementations.

What is claimed is:
 1. A substrate processing system comprising: aprocessing chamber having an exterior wall with a transparent portionand an interior portion; a pedestal to support a work piece disposedwithin the interior portion, the pedestal comprising a rigidly attachedfirst ring that is nearly concentric with a second ring, the second ringbeing rigidly attached to the processing chamber; and an opticalmeasurement assembly disposed outside of the processing chamber andcoupled to the exterior wall, the optical measurement assemblycomprising a laser gauge that supplies light and detects the suppliedlight after being reflected; wherein the laser gauge, the first ring,and the second ring are disposed to allow light to be transmitted by thelaser gauge into the processing chamber through the transparent portion,and to detect reflected light from the first ring and the second ring bythe laser gauge; wherein the optical measurement assembly comprises aprocessor that calculates a height difference between the first ring andthe second ring at a plurality of locations around a circumference ofthe pedestal.
 2. The substrate processing system of claim 1 wherein thetransparent portion is a quartz dome.
 3. The substrate processing systemof claim 1 wherein the transparent portion is a view port.
 4. Thesubstrate processing system of claim 1 wherein the pedestal is asusceptor.
 5. A substrate processing system comprising: a processingchamber having an exterior wall with a transparent portion and aninterior portion; a pedestal disposed within the processing chamber, thepedestal to support a work piece disposed within the interior portion,the pedestal comprising a rigidly attached first ring that is nearlyconcentric with a second ring, the second ring being rigidly attached tothe processing chamber; an optical measurement assembly coupled to anexterior of the processing chamber, wherein the optical measurementassembly comprises a laser gauge that supplies light and detects thesupplied light after being reflected; wherein the laser gauge, the firstring, and the second ring are disposed to allow light to be transmittedby the laser gauge into the processing chamber through the transparentportion and to detect reflected light from the first ring and the secondring by the laser gauge; wherein the optical measurement assemblydetermines a lateral location, a height and a tilt of the pedestal bytransmitting light into the processing chamber through the transparentportion of the processing chamber and detecting a reflected light afterthe reflected light leaves the chamber through the transparent portionof the processing chamber; wherein the first ring and the second ringare exposed to light from the laser gauge disposed outside of theprocessing chamber through the transparent portion of the chamber; alateral adjustment assembly to change the lateral location of thepedestal relative to the second ring; a vertical adjustment assembly tochange the height and the tilt of the pedestal relative to the secondring; wherein the optical measurement assembly comprises a processorthat determines the lateral location, the height and the tilt of thepedestal based on a height difference between the first ring and thesecond ring at a plurality of locations around a circumference of thepedestal; wherein the lateral adjustment assembly and the verticaladjustment assembly are outside of the processing chamber and arecoupled to the pedestal through a pedestal shaft, wherein the pedestalshaft is coupled to the processing chamber through a bellows.
 6. Thesubstrate processing system of claim 5 wherein the portion of theprocessing chamber that is transparent is a quartz dome.
 7. Thesubstrate processing system of claim 5 wherein the portion of theprocessing chamber that is transparent is a view port.
 8. The substrateprocessing system of claim 5 wherein the pedestal is a susceptor.
 9. Thesubstrate processing system of claim 5 wherein the lateral adjustmentassembly comprises three or more adjustment screws nearly equally spacedaround the second ring.
 10. The substrate processing system of claim 9wherein at least one of the three or more adjustment screws have tworegions with different thread pitches to produce a reduced apparentthread pitch.
 11. The substrate processing system of claim 9 wherein thebellows maintains a pressure difference between the inside and outsideof the substrate processing system while the lateral location of thepedestal is changed by adjusting at least one of the three or moreadjustment screws.
 12. The substrate processing system of claim 5further comprising a locking mechanism.
 13. The substrate processingsystem of claim 12 wherein the locking mechanism comprises one or moreset screws.
 14. A method of adjusting a position of a pedestalcomprising: determining a tilt and a location of the pedestal relativeto a processing system reference, wherein the pedestal comprises arigidly attached first ring that is nearly concentric with theprocessing system reference, the processing system reference is rigidlyattached to a processing system; leveling the pedestal in response tothe determined tilt to reduce the tilt of the pedestal relative to theprocessing system reference; and positioning the pedestal to be at apredetermined location in response to the determined location withoutsignificantly affecting the tilt; wherein the tilt and the location ofthe pedestal is determined by reflecting light from a plurality oflocations around the first ring and the processing system reference andanalyzing a reflected light to determine an indication of location ofthe first ring relative to the processing system reference at theplurality of locations around a circumference of the first ring.
 15. Themethod of claim 14 wherein the indication of location comprises adifference in height between the first ring and the processing systemreference.
 16. The method of claim 14 wherein the indication of locationcomprises a separation between an outer edge of the first ring and aninner edge of the processing system reference.
 17. The method of claim14 wherein reflecting light from a plurality of locations comprisesreflecting light from at least two locations to determine whether thepedestal is centered within the processing system reference.
 18. Themethod of claim 14 wherein reflecting light from a plurality oflocations comprises reflecting light from at least three locations todetermine a height and a lateral location of the pedestal.
 19. Themethod of claim 14 wherein reflecting light from a plurality oflocations comprises reflecting light from at least three locations todetermine the tilt of the pedestal.
 20. The method of claim 14 whereinanalyzing the reflected light further comprises calculating a tilt anglefrom a height difference between the first ring and the processingsystem reference.